This invention relates to a switching apparatus arranged for effective utilization of a regenerative repeater.
The switching apparatus is used to transmit voice signals, data signals and facsimile signals by selectively connecting a plurality of terminal devices. For transmission and reception of these signals, it has been demanded to shorten a length of time required for transmission of signals. To this end, there has been developed a modulation-demodulation device used, for example, with a voice band circuit which is operated at the signaling speed of 9600 bauds per second. However, the higher the transmission speed, the more noticeable the rate of data errors. This data error rate is largely affected by the quality of lines through which the signals are transmitted. Hitherto, the following processes have been adopted to keep the data error rate within an allowable limit. The usual upper limit of this error rate is, for example, 10.sup.-5. A first process is to lower a transmission rate to such extent that the data error rate can be reduced to a lower level than allowed even when a transmission line has the worst data error rate. However, this process goes contrary to the demand to accelerate transmission speed and is practically unacceptable. A second process is to connect a regenerative repeater to all output or outgoing circuits of the respective switching apparatus through which high error rate signals are expected to pass. This process connects a regenerative repeater to all outgoing circuits of the respective switching apparatus, at least a regenerative repeater is wasted when at least two regenerative repeaters are connected in a transmission path. Moreover, the regenerative repeater is generally costly to render the switching apparatus of the second process extremely expensive. Since it is rarely that all circuits of high error rate of signals are in use, the use of the expensive regenerative repeaters makes the switching apparatus very expensive.